(i) 21b – 32 + 7b – 20b
(re-arranging the terms)
= 21b + 7b – 20b – 32
= 28b – 20b – 32
= 8b – 32
(ii) z2 + 13z2 – 5z + 7Z2 – 15z
(re-arranging the terms)
= -z2 + 13z2 – 5z – 15z + 7z3
= 12z2 – 20z + 7z3
(iii) p – (p – q) – q – (q – p)
= p – p + q – q – q + p
(re-arranging the terms)
= p + p - p + q - q - q
= p – q
(iv) 3a – 2b – ab – (a – b + ab) + 3ab + b – a
= 3a – 2b – ab – a + b – ab + 3ab + b – a
= 3a – a – a – 2b + b + b – ab – ab + 3ab
= 3a - 2a - 2b + 2b - 2ab + 3ab
= a + ab
(v) 5x2y – 5x2 + 3yx2 – 3y2 + x2 – y2 + 8xy2 – 3y2
(re-arranging the terms)
= 5x2y + 3yx2 – 5x2 + x2 – 3y2 – y2 – 3y2 + y2
= 8x2y – 4x2 – 7y2 + 8xy2
(vi) (3y2 + 5y – 4) – (8y – y2 – 4) .
3y2 + 5y – 4 – 8y – y2 – 4
(re-arranging the terms)
3y2 + y2 + 5y – 8y – 4 + 4
= 14y2 – 3y